南海大气温室效应纬向地带性的遥感观测

REMOTE SENSING OBSERVATION OF THE LATITUDINAL ZONALITY FOR GREENHOUSE EFFECT IN THE SOUTH CHINA SEA REGION

本文选取位于入射太阳辐射能量峰值所在的绿光通道（MODIS卫星4通道）,以及位于可太阳耀光探测长波辐射区间的中红外通道（MODIS卫星21通道）为观测窗口对,遥感测量2000～2010年间南海研究区和东海对照区内,不同纬度带的大气典型短波与长波通道的太阳耀光辐射比参数（引入晴空辐射平衡的描述性指标CSRR,即Calibrated Sunglint Radiation Ratio）时间序列.据此大气双程透射率比及太阳分谱辐照度比的相关函数CSRR,了解南海大气温室效应纬向地带性的演变特征.经验模态分解方法分析结果表明,南海的大气温室效应包含3个相对重要的分量：1）由低纬往中纬逐渐增大的,受具有明显纬向地带性的水汽大储库与纬向地带性较弱的CO2小储库联合影响的长期变化趋势;2）受CO2、CH4、O3和气溶胶共同调控的准十年尺度分量;3）从低纬往中纬逐渐由双峰转变为单峰分布的年尺度分量.由此可见,关于地球-大气系统辐射平衡物理学参数地带性分布规律的观测,有助于理解从辐射强迫到温度变化的气候响应机制,对如何筛选简洁合理的第四纪气候评估模型具有参考价值.

In the present study, the Calibrated Sunglint Radiation Ratio （CSRR）, a descriptive index of clear-sky Radiance Balance was established using the calibrated ratio of the sunglint radiation differences of the green light band （MODIS CH4） and the middle infrared band （MODIS CH21）. The former is close to the peak wavelength of the incident solar radiation, and the latter detects sunglint in the region of outgoing long wave radiation. CSRR is a function concerning bidirectional atmospheric transmissivity ratio and solar irradiance ratio, which is capable to reveal the characteristics of the latitudinal variation of greenhouse effect in the South China Sea （SCS）. We calculated the time series of CSRR of various latitude zones in the SCS and the contrasting area （the East China Sea, ECS） from 2000 to 2010. Based on Empirical Mode Decomposition （EMD） analysis of the time series of CSRR, combined with remote sensing products including CH4, 03, CO2 and AOT （Aerosol Optical Thickness）, we found that there were three relative important components for greenhouse effect in the SCS. （1） On a long-term scale, the greenhouse effect in the Eastern Asian Seas appeared increasing growth from low latitudes to middle latitudes, which were affected mainly by both water vapor and CO2. In contrast to CO2, water vapor had large reservoirs in the atmosphere and contributed significantly to the latitudinal variation. （2） Over the SCS, greenhouse effect contained oscillation characteristic of quasi-10a cycles, with the low value appearing from 2005 to 2006. This distribution pattern was similar to the atmosphere components of CH4 , 03 and C02, which had a positive radiative forcing. AOT had negative radiative forcing and reverse-phase distribution. The quasi-10a cycle characteristic of greenhouse effect were co-regulated of CH4, O3 , CO2 and aerosol. （3） At an annual scale, greenhouse effect showed a bimodal distribution at 5°N, with the maximum/ minimum values being appearing in the spring, autumn/summer and winter seasons. At 10°N, the bimodal distribution of greenhouse effect still existed from 2000 to 2001. In the rest years for the 10°N belt, and at 15°N and 20°N, it was transformed gradually into the unimodal distribution, with the maximum values being appearing in the summer seasons. The annual cycle characteristic of greenhouse effect were co-regulated of CH4 , 03 , CO2 and aerosol, and the aerosol was the main driving factor in the transformation between unimodal and bimodal distributions. Thus, the observation of the zonation distribution of physical parameters associated with radiation balance helps to understand the climate response mechanism, from radiative forcing to temperature changes, which is useful in improving the climate models for the region.